Arthur Kantrowitz passed away on November 29, 2008 in New York City. He was 95 years old. A founder of Avco Everett Research Laboratories, inventor of ablative rocket nose cones (reentry protection), champion of Science Court and professor of Dartmouth College, Kantrowitz will be always remembered as a forefront figure of American scientific community of 20th century. However, in this brief note I would like to say few words about one of his greatest contributions to mankind: his key role in development of laser propulsion.
It is rocket science, but forget the silly cliché: the idea of laser propulsion is simple. Modern space rockets are too heavy, inefficient, and dangerous, because they have to carry their fuel and oxidizer onboard. On average they cost us $10,000 per pound of a payload delivered to low earth orbit. If someone could find a way to separate the energy source from a rocket, which will eliminate all fuel-related burden, the gain in rocket efficiency will be enormous.
This can be done using energy transfer with laser beams! This idea was originally formulated in 1924 by Konstantin Tsiolkovsky, who believed that beams of light could serve as a source of external energy for driving space rockets, that removed the burden of fuel onboard and makes rocket much lighter, and hence, more efficient. Tsiolkovsky with his pioneering ideas forerun his time on at least 50 years, Kantrowitz who was 11 years old in 1924, made his pioneering contribution just in time.
In 1972 Kantrowitz published a paper titled “Propulsion to Orbit by Ground Based Lasers”, with a genius idea: to launch light satellites right from the ground to space with high-power laser beams. In this the vehicle will be just “straddling” the tip of the beam. When laser beam is focused on a solid surface, it has enough power to vaporize and ionize almost anything with energy release much higher than hydrogen burning, used in modern space rockets. So, comparing to chemical rockets, laser propulsion uses the same rocket principle, excepting much more energetic exhaust and much lighter vehicle structure: no tanks, fuel lines, etc. leaving a lot of room for a payload.
Laser-propelled rockets will be made of light focusing optics (mirrors), modest amount of ablative solid fuel, and the rest is a payload. No more need for heavy fuel/oxidizer, tanks, lines, chambers, nozzles! Kantrowitz called it 4P Principle: Payload, Propellant and Photons, Period! Scientifically proven (and repeated in different ways for many times) calculations show that with the laser propulsion space delivery price will be reduced to $100 per pound of a payload! It is hundredfold savings!
The paper of Dr. Kantrowitz from 1972 marked the beginning of a new scientific quest. In early seventies Kantrowitz has initiated first research program on laser propulsion at Avco-Everett Research Labs, which for over a decade was the only research program in this field in the world. Later other projects ensued, first laser-propelled vehicles were launched (not into space yet, but high enough to prove the viability of an idea), other countries (Russia, Japan, Germany, China) and hundreds of scientists and engineers joined the quest for laser propulsion (and other forms of beamed-energy propulsion, such as microwave propulsion). However, we should always remember one man who started it all: Arthur Kantrowitz, the father of laser propulsion.